Eosinophilia

Eosinophilia is an increase in the number of eosinophils in the peripheral blood of more than 450 / µl. There are many reasons for increasing the number of eosinophils, but more often there is an allergic reaction or parasitic infections. Diagnosis is a selective survey directed to a clinically suspected cause. Treatment is focused on the elimination of the underlying disease.

Eosinophilia has features of an immune response: an agent such as Trichinella spiralis promotes the development of a primary reaction with a relatively low level of eosinophils, the reappearance of the agent leads to an increase in the level of eosinophils or a secondary eosinophilic response.

Factors that reduce the number of eosinophils include beta-blockers, glucocorticoids, stress, and sometimes bacterial or viral infections. Some mast cell-released structures induce IgE-mediated eosinophil production, for example, eosinophilic chemotactic anaphylaxis factor, leukotriene B4, complement complex (C5-C6-C7) and histamine (above normal concentration).

Eosinophilia can be primary (idiopathic) or secondary in multiple diseases. In the USA, the most common causes of eosinophilia are allergic and atopic diseases, among which respiratory and skin diseases are more common. Almost all parasitic tissue invasions can cause eosinophilia, but damage by simple and non-invasive multicellular ones is usually not accompanied by an increase in the level of eosinophils.

Neoplastic diseases, Hodgkin's lymphoma can cause significant eosinophilia, which is not typical of non-Hodgkin's lymphoma, chronic myeloid leukemia and acute lymphoblastic leukemia. Among solid tumors, ovarian cancer is the most common cause of eosinophilia. Hyper-eosinophilic syndrome with lesions of the lungs includes a spectrum of clinical manifestations characterized by peripheral eosinophilia and eosinophilic pulmonary infiltrates, but the etiology is usually unknown. Patients with eosinophilic drug reactions may not have any clinical symptoms or have manifestations of various syndromes, including interstitial nephritis, serum sickness, cholestatic jaundice, hypersensitive vasculitis and immunoblastic lymphadenopathy. Several hundred patients with eosinophilic myalgia syndrome have been reported after taking L-tryptophan for sedation or psychotropic therapy. This syndrome is probably caused not by L-tryptophan itself, but by contamination. Symptoms (marked muscle pain, tendinovinit, muscle swelling, skin rash) lasted from a week to months, there were fatal cases.

[1], [2], [3], [4], [5]

The main causes of secondary eosinophilia

The reasons	Examples
Allergic or atopic diseases	Asthma, allergic rhinitis, allergic bronchopulmonary aspergillosis, occupational lung diseases, urticaria, eczema, atopic dermatitis, milk protein allergy, angioedema with eosinophilia, drug reaction
Parasitic infections (especially multicellular with tissue invasion)	Trichinosis, visceral syndrome of the “wandering larva”, trichiuriasis, ascariasis, strongyloidosis, cysticercosis (Taenia solium), echinococcosis, filariasis, schistosomiasis, nematodes, Pneumocystis jiroveci (formerly P. Carinii)
Nonparasitic infections	Aspergillosis, brucellosis, cat scratch disease, infectious lymphocytosis, chlamydial pneumonia in infants, acute coccidioidomycosis, infectious mononucleosis, mycobacterial diseases, scarlet fever
Tumors	Cancer and sarcomas (lung, pancreas, colon, cervix, ovaries), Hodgkin lymphoma, non-Hodgkin lymphomas, immunoblastic lymphadenopathy
Myeloproliferative diseases	Chronic myeloid leukemia
Pulmonary Infiltration Syndromes with Eosinophilia	Simple pulmonary eosinophilia (Leffler syndrome), chronic eosinophilic pneumonia, tropical pulmonary eosinophilia, allergic bronchopulmonary aspergillosis, Churg-Strauss syndrome
Skin diseases	Exfoliative dermatitis, herpetiform dermatitis, psoriasis, pemphigus
Connective tissue diseases or granulomatous diseases (especially involving the lungs)	Nodular polyarthritis, rheumatoid arthritis, sarcoidosis, inflammatory bowel disease, SLE, scleroderma, eosinophilic fasciitis
Immune diseases	Graft-versus-host disease, congenital immunodeficiency syndrome (eg, IgA deficiency, hyper lgA syndrome, Wiskott-Aldrich syndrome)
Endocrine diseases	Adrenal hypofunction
Various	Cirrhosis, radiation therapy, peritoneal dialysis, familial eosinophilia, use of L-tryptophan

Diagnosis and treatment of eosinophilia

When eosinophilia is present in a peripheral blood test, it is often not necessary to calculate the absolute number of eosinophils. It is necessary to clarify the history, especially information about travel, allergies and the use of medicines, then examine the patient. The feasibility of performing specific diagnostic tests is determined on the basis of inspection data and may include chest X-rays, urinalysis, liver and kidney function tests, and serological tests for the presence of parasitic infections and connective tissue diseases. An analysis of feces for the identification of parasites and their eggs is required, although a negative result does not exclude the absence of a parasitic infection (for example, trichinosis requires a muscle biopsy; migratory visceral larvae and filarial infections require a biopsy of other tissues; duodenal aspirate is necessary to exclude specific parasites, for example Strongyloides sp ). Elevated levels of serum vitamin B ₁₂, or low alkaline phosphatase leukocytes, or abnormalities in the peripheral blood smear suggest a myeloproliferative disease in which research is needed, and bone marrow aspirate biopsies with cytogenetic analyzes.

If the cause of eosinophilia is not found, the patient is threatened with complications. The test with a short prescription of low doses of glucocorticoids will demonstrate a decrease in the number of eosinophils if the eosinophilia is secondary (for example, an allergy or parasitic infection), and will not have an effect on cancer. Conducting such a test is indicated for continuous or progressive eosinophilia and no apparent cause.

[6], [7], [8], [9], [10]